Go is an open source project, distributed under a BSD-style license. This document explains how to check out the sources, build them on your own machine, and run them.
Most users don't need to do this, and will instead install from precompiled binary packages as described in Getting Started, a much simpler process. If you want to help develop what goes into those precompiled packages, though, read on.
There are two official Go compiler tool chains.
This document focuses on the gc Go
compiler and tools (6g, 8g etc.).
For information on how to work on gccgo, a more traditional
compiler using the GCC back end, see
Setting up and using gccgo.
The Go compilers support three instruction sets. There are important differences in the quality of the compilers for the different architectures.
amd64 (a.k.a. x86-64); 6g,6l,6c,6a
gccgo can do noticeably better sometimes).
386 (a.k.a. x86 or x86-32); 8g,8l,8c,8a
amd64 port.
arm (a.k.a. ARM); 5g,5l,5c,5a
Except for things like low-level operating system interface code, the run-time support is the same in all ports and includes a mark-and-sweep garbage collector, efficient array and string slicing, and support for efficient goroutines, such as stacks that grow and shrink on demand.
The compilers can target the DragonFly BSD, FreeBSD, Linux, NetBSD, OpenBSD, OS X (Darwin), Plan 9, Solaris and Windows operating systems. The full set of supported combinations is listed in the discussion of environment variables below.
The Go tool chain is written in C. To build it, you need a C compiler installed. Please refer to the InstallFromSource page on the Go community Wiki for operating system specific instructions.
To perform the next step you must have Mercurial installed. (Check that you
have an hg command.)
If you do not have a working Mercurial installation, follow the instructions on the Mercurial downloads page.
Mercurial versions 1.7.x and up require the configuration of Certification Authorities (CAs). Error messages of the form:
warning: code.google.com certificate with fingerprint b1:af: ... bc not verified (check hostfingerprints or web.cacerts config setting)
when using Mercurial indicate that the CAs are missing.
Check your Mercurial version (hg --version) and
configure the CAs
if necessary.
Go will install to a directory named go.
Change to the directory that will be its parent
and make sure the go directory does not exist.
Then check out the repository:
$ hg clone -u release https://code.google.com/p/go
If you intend to modify the go source code, and contribute your changes to the project, then move your repository off the release branch, and onto the default (development) branch. Otherwise, skip this step.
$ hg update default
To build the Go distribution, run
$ cd go/src $ ./all.bash
(To build under Windows use all.bat.)
If all goes well, it will finish by printing output like:
ALL TESTS PASSED --- Installed Go for linux/amd64 in /home/you/go. Installed commands in /home/you/go/bin. *** You need to add /home/you/go/bin to your $PATH. ***
where the details on the last few lines reflect the operating system, architecture, and root directory used during the install.
For more information about ways to control the build, see the discussion of
environment variables below.
all.bash (or all.bat) runs important tests for Go,
which can take more time than simply building Go. If you do not want to run
the test suite use make.bash (or make.bat)
instead.
Check that Go is installed correctly by building a simple program.
Create a file named hello.go and put the following program in it:
package main
import "fmt"
func main() {
fmt.Printf("hello, world\n")
}
Then run it with the go tool:
$ go run hello.go hello, world
If you see the "hello, world" message then Go is installed correctly.
You're almost done. You just need to do a little more setup.
How to Write Go Code Learn how to set up and use the Go tools
The How to Write Go Code document provides essential setup instructions for using the Go tools.
The source code for several Go tools (including godoc)
is kept in the go.tools repository.
To install all of them, run the go get command:
$ go get code.google.com/p/go.tools/cmd/...
Or if you just want to install a specific command (godoc in this case):
$ go get code.google.com/p/go.tools/cmd/godoc
To install these tools, the go get command requires
that Mercurial be installed locally.
You must also have a workspace (GOPATH) set up;
see How to Write Go Code for the details.
Note: The go command will install the godoc
binary to $GOROOT/bin (or $GOBIN) and the
cover and vet binaries to
$GOROOT/pkg/tool/$GOOS_$GOARCH.
You can access the latter commands with
"go tool cover" and
"go tool vet".
The usual community resources such as
#go-nuts on the Freenode IRC server
and the
Go Nuts
mailing list have active developers that can help you with problems
with your installation or your development work.
For those who wish to keep up to date,
there is another mailing list, golang-checkins,
that receives a message summarizing each checkin to the Go repository.
Bugs can be reported using the Go issue tracker.
The Go project maintains a stable tag in its Mercurial repository:
release.
The release tag refers to the current stable release of Go.
Most Go users should use this version. New releases are announced on the
golang-announce
mailing list.
To update an existing tree to the latest release, you can run:
$ cd go/src $ hg pull $ hg update release $ ./all.bash
The Go compilation environment can be customized by environment variables. None is required by the build, but you may wish to set some to override the defaults.
$GOROOT
The root of the Go tree, often $HOME/go.
Its value is built into the tree when it is compiled, and
defaults to the parent of the directory where all.bash was run.
There is no need to set this unless you want to switch between multiple
local copies of the repository.
$GOROOT_FINAL
The value assumed by installed binaries and scripts when
$GOROOT is not set explicitly.
It defaults to the value of $GOROOT.
If you want to build the Go tree in one location
but move it elsewhere after the build, set
$GOROOT_FINAL to the eventual location.
$GOOS and $GOARCH
The name of the target operating system and compilation architecture.
These default to the values of $GOHOSTOS and
$GOHOSTARCH respectively (described below).
Choices for $GOOS are
darwin (Mac OS X 10.6 and above), dragonfly, freebsd,
linux, netbsd, openbsd,
plan9, solaris and windows.
Choices for $GOARCH are
amd64 (64-bit x86, the most mature port),
386 (32-bit x86), and arm (32-bit ARM).
The valid combinations of $GOOS and $GOARCH are:
$GOOS | $GOARCH |
|
|---|---|---|
darwin | 386 |
|
darwin | amd64 |
|
dragonfly | 386 |
|
dragonfly | amd64 |
|
freebsd | 386 |
|
freebsd | amd64 |
|
freebsd | arm |
|
linux | 386 |
|
linux | amd64 |
|
linux | arm |
|
netbsd | 386 |
|
netbsd | amd64 |
|
netbsd | arm |
|
openbsd | 386 |
|
openbsd | amd64 |
|
plan9 | 386 |
|
plan9 | amd64 |
|
solaris | amd64 |
|
windows | 386 |
|
windows | amd64 |
$GOHOSTOS and $GOHOSTARCH
The name of the host operating system and compilation architecture. These default to the local system's operating system and architecture.
Valid choices are the same as for $GOOS and
$GOARCH, listed above.
The specified values must be compatible with the local system.
For example, you should not set $GOHOSTARCH to
arm on an x86 system.
$GOBIN
The location where Go binaries will be installed.
The default is $GOROOT/bin.
After installing, you will want to arrange to add this
directory to your $PATH, so you can use the tools.
If $GOBIN is set, the go command
installs all commands there.
$GO386 (for 386 only, default is auto-detected
if built natively, 387 if not)
This controls the code generated by 8g to use either the 387 floating-point unit
(set to 387) or SSE2 instructions (set to sse2) for
floating point computations.
GO386=387: use x87 for floating point operations; should support all x86 chips (Pentium MMX or later).
GO386=sse2: use SSE2 for floating point operations; has better performance than 387, but only available on Pentium 4/Opteron/Athlon 64 or later.
$GOARM (for arm only; default is auto-detected if building
on the target processor, 6 if not)
This sets the ARM floating point co-processor architecture version the run-time should target. If you are compiling on the target system, its value will be auto-detected.
GOARM=5: use software floating point; when CPU doesn't have VFP co-processor
GOARM=6: use VFPv1 only; default if cross compiling; usually ARM11 or better cores (VFPv2 or better is also supported)
GOARM=7: use VFPv3; usually Cortex-A cores
If in doubt, leave this variable unset, and adjust it if required when you first run the Go executable. The GoARM page on the Go community wiki contains further details regarding Go's ARM support.
Note that $GOARCH and $GOOS identify the
target environment, not the environment you are running on.
In effect, you are always cross-compiling.
By architecture, we mean the kind of binaries
that the target environment can run:
an x86-64 system running a 32-bit-only operating system
must set GOARCH to 386,
not amd64.
If you choose to override the defaults,
set these variables in your shell profile ($HOME/.bashrc,
$HOME/.profile, or equivalent). The settings might look
something like this:
export GOROOT=$HOME/go export GOARCH=amd64 export GOOS=linux
although, to reiterate, none of these variables needs to be set to build, install, and develop the Go tree.